文章评述了施密特光学系统发明以来的四种深空天图，它们是帕洛玛天图、ESO/SRC南天天图、帕洛玛银道带红外天图和南天红外天图。
It describes 4 deep-sky surveys since the discovering of Schmidt optics . They are Palomar Observatory Sky Survey , ESO / SRC Atlas of the Southern Sky , Palomar Infrared Milky Way Atlas , and UK Schmidt Southern I / SR Atlas .
四空天